Has anyone else experimented with the vibrations you feel when going through the typical SP / WILD scenario?

Lately I have been experimenting with that vibrating feeling. I find that I can amplify or dampen the feeling by flexing with my mind. I feel I have pretty good control over it. Does anyone know of any good information about what this vibrating feeling actually is?

Last night I was in SP and was trying to push the vibrations to the highest level possible. I have never felt anything so intense. It felt like my head was going to explode. I don't want to give myself a stroke or something.

I know that people who subscribe to the Astral Projection theory of things do a lot of work with these vibrations. Besides that, are there any good theories about whats going on here?